U.S. patent application number 14/409541 was filed with the patent office on 2015-06-25 for battery pack.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Takashi Harayama.
Application Number | 20150180004 14/409541 |
Document ID | / |
Family ID | 49768510 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150180004 |
Kind Code |
A1 |
Harayama; Takashi |
June 25, 2015 |
BATTERY PACK
Abstract
A battery pack has a plurality of series-connected batteries
each having an electrode body, a battery case, a positive extending
member, a positive external terminal mechanically joined and
electrically connected to a positive external extending part of the
positive extending member, by caulking deformation thereof, a
negative extending member, and a negative external terminal
mechanically joined and electrically connected to a negative
external extending part of the negative extending member, by
caulking deformation thereof. Among the positive and negative
external extending parts, the positive and negative external
terminals, the metal making up the positive external extending part
has the lowest tensile strength. The battery pack includes bus
bars; positive fastening members for fastening the positive
external terminals to the bus bars; and negative fastening members
for fastening the negative external terminals to the bus bars. The
negative external terminal is thinner than the positive external
terminal.
Inventors: |
Harayama; Takashi;
(Toyota-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi, Aichi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi
JP
|
Family ID: |
49768510 |
Appl. No.: |
14/409541 |
Filed: |
April 24, 2013 |
PCT Filed: |
April 24, 2013 |
PCT NO: |
PCT/JP2013/061980 |
371 Date: |
December 19, 2014 |
Current U.S.
Class: |
429/158 |
Current CPC
Class: |
H01M 2/202 20130101;
H01M 2/06 20130101; H01M 2/206 20130101; H01M 2/26 20130101; Y02E
60/10 20130101; H01M 2/08 20130101; H01M 2220/30 20130101; H01M
2/204 20130101; H01M 2220/20 20130101; H01M 2/30 20130101 |
International
Class: |
H01M 2/20 20060101
H01M002/20; H01M 2/30 20060101 H01M002/30; H01M 2/08 20060101
H01M002/08; H01M 2/26 20060101 H01M002/26; H01M 2/06 20060101
H01M002/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2012 |
JP |
2012-140024 |
Claims
1. A battery pack comprising a plurality of batteries connected in
series, each of the batteries including: an electrode body; a
battery case housing the electrode body; a positive extending
member made of metal and connected to a positive electrode of the
electrode body in the battery case and extended out of the battery
case by penetrating through the battery case; a positive external
terminal made of a metal plate, placed outside the battery case,
and mechanically joined to a positive external extending part of
the positive extending member, the positive external extending part
being located outside the battery case and deformed by caulking to
fix the positive external terminal to the battery case, the
positive external terminal being electrically connected to the
positive external extending part; a negative extending member made
of metal and connected to a negative electrode of the electrode
body in the battery case and extended out of the battery case by
penetrating through the battery case; and a negative external
terminal made of a metal plate, placed outside the battery case,
and mechanically joined to a negative external extending part of
the negative extending member, the negative external extending part
being located outside the battery case and deformed by caulking to
fix the negative external terminal to the battery case, the
negative external terminal being electrically connected to the
negative external extending part, among metals forming the positive
external extending part of the positive extending member, the
positive external terminal, the negative external extending part of
the negative extending member, and the negative external terminal,
the metal forming the positive external extending part of the
positive extending member has lowest tensile strength, wherein the
battery pack includes: bus burs each placed between the positive
external terminal of one of the batteries and the negative external
terminal of an other battery to connect the positive external
terminal and the negative external terminal; a positive fastening
member fastening the positive external terminal of the one battery
to the bus bar; and a negative fastening member fastening the
negative external terminal of the other battery to the bus bar,
each of the batteries is configured such that the negative external
terminal has a thinner plate thickness than a plate thickness of
the positive external terminal.
2. The battery pack according to claim 1, wherein the metal forming
the negative external terminal is a material having higher
electrical conductivity than the metal forming the positive
external terminal.
3. The battery pack according to claim 2, wherein the metal forming
the positive external extending part of the positive extending
member is pure aluminum, the metal forming the positive external
terminal is aluminum alloy, and both the metal forming the negative
external extending part of the negative extending member and the
metal forming the negative external terminal are pure copper.
Description
TECHNICAL FIELD
[0001] The present invention relates to a battery pack including a
plurality of batteries connected in series.
BACKGROUND ART
[0002] Recently, chargeable-dischargeable batteries are utilized as
drive power sources of vehicles such as a hybrid car and an
electric car or drive power sources of portable electronic devices
such as a note-sized personal computer and a video camcorder. As
one example of such batteries, Patent Document 1 discloses a
battery including a power generating element, a battery case that
houses the power generating element, and an electrode terminal
member having an element connecting member penetrating through the
battery case, an externally-located terminal member connected to
the element connecting member, and a fastening member. This
externally-located terminal member of the battery has a Z-like
shape (a crank-like shape) including a fixed part, an intermediate
part, and an outer connecting part. The element connecting member
penetrates through the fixed part and a male screw part of the
fastening member penetrates through the outer connecting part,
respectively. On a positive electrode side, the element connecting
member is made of pure aluminum, and a portion located outside the
battery case, of this connecting member, is deformed by caulking or
riveting to mechanically join the element connecting member to the
externally-located terminal member and fix the externally-located
terminal member to the battery case. On a negative electrode side,
on the other hand, the element connecting member is made of pure
copper, and a portion located outside the battery case, of this
connecting member, is deformed by caulking or riveting to
mechanically join the element connecting member to the
externally-located terminal member and fix this externally-located
terminal member to the battery case.
RELATED ART DOCUMENTS
Patent Documents
[0003] Patent Document 1: JP-A-2011-23142
SUMMARY OF INVENTION
Problems to be Solved by the Invention
[0004] Meanwhile, when a plurality of the batteries disclosed in
Patent Document 1 are assembled into a battery pack, in many cases,
a bus bar is interposed between the externally-located terminal
member (a positive external terminal) on a positive electrode side
(positive-side) of one of the batteries and the externally-located
terminal member (a negative external terminal) on a negative
electrode side (negative-side) of the other battery to connect
them. To be concrete, with use of the aforementioned fastening
members having the male screw parts and nuts, the positive-side
externally-located terminal member (the positive external terminal)
and the bus bar are fastened to each other or the bus bar and the
negative-side externally-located terminal member (the negative
external terminal) are fastened to each other.
[0005] Patent Document 1 does not particularly specify the
materials of the positive-side externally-located terminal member
(the positive external terminal) and the negative-side
externally-located terminal member (the negative external
terminal). However, if the positive external terminal is made of
pure aluminum, it is likely to buckle due to fastening with the bus
bar. Therefore, many of positive external terminals are made of
aluminum alloy such as Al--Mg, higher in tensile strength than pure
aluminum. On the other hand, many of negative external terminals
are made of pure copper (tough pitch copper) the same as the
negative-side element connecting member (the negative extending
member). Accordingly, the tensile strength of the pure copper
forming the negative extending member and the negative external
terminal is higher than the tensile strength of the pure aluminum.
Specifically, the metal forming the positive-side element
connecting member (the positive extending member) has the lowest
tensile strength.
[0006] When the batteries mentioned above are connected in series
to assemble a battery pack, the positive external terminal of one
of two batteries is fastened to the bus bar, and this bus bar is
fastened to the negative external terminal of the other battery as
mentioned above. However, the positions of the positive external
terminal, negative external terminal, and bus bar may be displaced
as compared with an ideal position due to dimensional tolerance and
assembling error of the positive external terminal, negative
external terminal, bus bar, or battery case. Therefore, when the
positive external terminal, the negative external terminal, and the
bus bar are fastened together, the positive external terminal, the
negative external terminal, or the bus bar is apt to be deformed in
association with the displacement. When stress is applied to the
positive external extending parts deformed by caulking of the
positive electrode sheet connection made of pure aluminum lower in
tensile strength through the positive external terminal, this
caulked portion may undergo plastic deformation, thus loosening the
caulking state.
[0007] The present invention has been made to solve the above
problems and has a purpose to provide a battery pack including a
battery configured to suppress loosening of a caulking state of a
positive external extending part, deformed by caulking, of a
positive extending member.
Means of Solving the Problems
[0008] To achieve the above purpose, one aspect of the invention
provides a battery pack comprising a plurality of batteries
connected in series, each of the batteries including: an electrode
body; a battery case housing the electrode body; a positive
extending member made of metal and connected to a positive
electrode of the electrode body in the battery case and extended
out of the battery case by penetrating through the battery case; a
positive external terminal made of a metal plate, placed outside
the battery case, and mechanically joined to a positive external
extending part of the positive extending member, the positive
external extending part being located outside the battery case and
deformed by caulking to fix the positive external terminal to the
battery case, the positive external terminal being electrically
connected to the positive external extending part; a negative
extending member made of metal and connected to a negative
electrode of the electrode body in the battery case and extended
out of the battery case by penetrating through the battery case;
and a negative external terminal made of a metal plate, placed
outside the battery case, and mechanically joined to a negative
external extending part of the negative extending member, the
negative external extending part being located outside the battery
case and deformed by caulking to fix the negative external terminal
to the battery case, the negative external terminal being
electrically connected to the negative external extending part,
among metals forming the positive external extending part of the
positive extending member, the positive external terminal, the
negative external extending part of the negative extending member,
and the negative external terminal, the metal forming the positive
external extending part of the positive extending member has lowest
tensile strength, wherein the battery pack includes: bus burs each
placed between the positive external terminal of one of the
batteries and the negative external terminal of an other battery to
connect the positive external terminal and the negative external
terminal; a positive fastening member fastening the positive
external terminal of the one battery to the bus bar; and a negative
fastening member fastening the negative external terminal of the
other battery to the bus bar, each of the batteries is configured
such that the negative external terminal has a thinner plate
thickness than a plate thickness of the positive external
terminal.
[0009] In the aforementioned battery pack, the negative external
terminal in each battery is made thinner in plate thickness than
the positive external terminal, so that the negative external
terminal is more likely to be deformed as compared to the case
where the negative external terminal is designed to have the same
plate thickness as the positive external terminal. Accordingly,
when one battery is connected to the other battery in series, for
example, as described above, even if the positive external
terminal, the negative external terminal, or the bus bar is
displaced in position from those in an ideal case, the stress
caused by fastening them can be absorbed by deformation of the
negative external terminal. Because of the negative external
terminal absorbs the stress, the stress applied to the positive
external extending part, deformed by caulking, of the positive
extending member can be reduced, and thus the plastic deformation
thereof can be suppressed. Consequently, the battery pack can be
achieved including the batteries in which the positive external
extending parts of the positive extending members are suppressed
from loosening their caulking state.
[0010] The shapes of the positive external terminal and the
negative external terminal, for example, may include a flat-plate
shape, an L-like shape, a Z-like shape (a crank-like shape) bent in
crank-like shape in a plate thickness direction, and others. The
positive external terminal and the negative external terminal may
be identical to or different from each other in shape. The metal
tensile strength is represented by a value measured in "JIS Z2241".
The materials of the positive extending member and the positive
external terminal can be selected from pure aluminum, aluminum
alloy, and others. Further, the materials of the negative extending
member and the negative external terminal can be selected from pure
copper, copper alloy, and others. However, the materials (metals)
of the positive external extending part, the positive external
terminal, the negative external extending part, and the negative
external terminal are combined so that the metal forming the
positive external extending part has the lowest tensile strength
among the metals forming the positive external extending part, the
positive external terminal, the negative external extending part,
and the negative external terminal.
[0011] In the aforementioned battery pack, preferably, the metal
forming the negative external terminal is a material having higher
electrical conductivity than the metal forming the positive
external terminal.
[0012] In the aforementioned battery pack, the metal forming the
negative external terminal has a higher electrical conductivity
than the metal forming the positive external terminal. Thus, the
resistance increase can be suppressed to be lower when the negative
external terminal is designed with a smaller plate thickness as
compared with when the positive external terminal is designed with
a smaller plate thickness. This makes it possible to achieve the
battery pack using the batteries low in conductive resistance as a
whole.
[0013] In the aforementioned battery pack, preferably, the metal
forming the positive external extending part of the positive
extending member is pure aluminum, the metal forming the positive
external terminal is aluminum alloy, and both the metal forming the
negative external extending part of the negative extending member
and the metal forming the negative external terminal are pure
copper.
[0014] In each battery mentioned above, the metal forming the
positive external extending part of the positive extending member
is made of pure aluminum, the metal forming the positive external
terminal is aluminum alloy, and all the metals forming the positive
external extending part of the negative extending member and the
negative external terminal are pure copper. Therefore, the
positive-side members (the positive extending member and the
positive external terminal) and the negative-side members (the
negative extending member and the negative external terminal) can
provide good electric conductive performance. Furthermore, since
the metal forming the positive external extending part of the
positive extending member is pure aluminum, and the metal forming
the negative external extending part of the negative extending
member is pure copper, the battery can be provided with the
positive external extending part and the negative external
extending part, each of which has been appropriately deformed by
caulking. In addition, the positive external terminal is made of
aluminum alloy and the negative external terminal is made of pure
copper, so that these positive and negative external terminals can
be appropriately prevented from buckling when fastened to the bus
bar.
[0015] The pure aluminum may be selected for example from alloy
numbers 1050, 1070, 1080, and 1085 listed in "JIS H4000". The
aluminum alloy may be selected for example from the alloy numbers
of 2000 series (Al--Cu alloy) such as 2014 and 2017, the alloy
numbers of 3000 series (Al--Mn alloy) such as 3003, 3103, the alloy
numbers of 5000 series (Al--Mg alloy) such as 5005 and 5021, the
alloy numbers of 6000 series (Al--Mg--Si alloy) such as 6101 and
6061, and the alloy numbers of 7000 series (Al--Zn--Mg alloy) such
as 7010 and 7075, listed in "JIS H4000". Further, the pure copper
may include oxygen-free copper having an alloy number C1020, tough
pitch copper having an alloy number C1100, or phosphorous
deoxidized copper having alloy numbers C1201, C1220, C1221, and
others, listed in "IS0197" (adopted corresponding to "JIS
H0500").
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view of a battery pack in an
embodiment;
[0017] FIG. 2 is an explanatory view (a partial enlarged end face
view) to explain connection between batteries of the battery pack
in the embodiment;
[0018] FIG. 3 is a vertical sectional view of the battery in the
embodiment;
[0019] FIG. 4 is an exploded perspective view of a lid member of
the battery in the embodiment; and
[0020] FIG. 5 is a vertical sectional view of a battery in a
comparative example.
MODE FOR CARRYING OUT THE INVENTION
Embodiment
[0021] A detailed description of a preferred embodiment of a
battery pack 1 embodying the present invention will now be given
referring to the accompanying drawings. FIG. 1 is a perspective
view of this battery pack 1. The battery pack 1 includes fifty
batteries 100, 100, bus bars 2, 2 each connecting the batteries 100
in series, plate-like members 3 alternately stacked with the
batteries 100, and two end plates (a first end plate 4 and a second
end plate 5) placed at both ends in a stacking direction DL by
sandwiching therebetween the batteries 100 and the plate-like
members 3. The battery pack 1 further includes nuts 9 cooperating
with positive bolts 139 (mentioned later) or negative bolts 149
(mentioned later) of the batteries 100 to fasten the bus bars 2 to
positive external terminals 137 (mentioned later) or negative
external terminals 147 (mentioned later). This battery pack 1
houses a plurality of the batteries 100, 100 arranged in a single
row in the stacking direction DL in a battery pack case 6. Of them,
the first end plate 4 and the second end plate 5, each being made
of metal and having a rectangular plate-like shape, are arranged at
both ends in the stacking direction DL of the batteries 100, 100 to
press against the batteries 100, 100 to suppress size change of the
batteries 100 in the stacking direction DL. Each of the plate-like
members 3 made of resin is provided, in each surface 3F contacting
with the corresponding battery 100, with a plurality of rectangular
strip-shaped recesses 3G extending perpendicular to the drawing
sheet of FIG. 2 which is a partial enlarged end face view showing a
section B in FIG. 1. These recesses 3G generate a plurality of
rectangular gaps S to allow air to flow between the battery 100 and
the plate-like member 3. By supplying cooling air to these gaps S,
the battery 100 can be cooled.
[0022] Each of the flat-plate bus bars 2 made of pure copper
(C1100) is formed with through holes 2H and 2H in both end areas
(see FIG. 2). In these through holes 2H and 2H, the positive bolt
139 (mentioned below) and the negative bolt 149 (mentioned below)
of the batteries 100 are inserted in connecting the batteries 100,
100 to each other. The battery pack 1 in the present embodiment is
configured such that the plurality of batteries 100, 100 are
connected in series, and the positive bolts 139 are inserted in
ones of the through holes 2H of the bus bars 2, while the negative
bolts 149 are inserted in the other through holes 2H (see FIG.
2).
[0023] Each of the batteries 100 is a lithium ion secondary battery
including an electrode body 150 and a battery case 100 housing this
electrode body 150. Each battery 100 is provided with a positive
extending member 130 connected with a positive electrode sheet 151
of the electrode body 150 in the battery case 110 and extended out
by penetrating through the battery case 110, and a positive
external terminal 137 placed outside the battery case 110. Further,
each battery 100 is provided with a negative extending member 140
connected with a negative electrode sheet 156 of the electrode body
150 in the battery case 110 and extended out by penetrating through
the battery case 110, and a negative external terminal 147 placed
outside the battery case 110. In addition to the above, there are
provided the positive bolts 139 located outside the battery case
110 and electrically connected (connectable) to the positive
external terminals 137 and the negative bolts 149 located outside
the battery case 110 and electrically connected (connectable) to
the negative external terminals 147. There are further provided
first insulating members 170 each located between the positive
extending member 130 or the negative extending member 140 and the
battery case 110, and second insulating members 180 each placed on
the battery case 110.
[0024] The battery case 110 includes a rectangular box-shaped case
body 111 having an opening 111d, and a plate-shaped lid member 113
closing the opening 111d of the case body 111. The case body 111
and the lid member 113 are made integral by welding. The lid member
113 has a rectangular plate-like shape and is formed with circular
through holes 113h and 113k each penetrating through the lid member
113 in its both end areas in a longitudinal direction (a right-left
direction in FIG. 3). The case lid 113 is further provided, at its
center in the longitudinal direction, with a safety valve 113j.
This safety valve 113j is formed integral with the case lid 113 to
constitute a part of the case lid 113. The case lid 113 is formed,
between the safety valve 113j and the through hole 113k, with a
liquid inlet 113n (see FIG. 3) through which electrolyte (not
shown) is poured into the battery case 110. This liquid inlet 113n
is sealed with a plug 113m.
[0025] This electrode body 150 is a wound electrode body of a
flattened shape including the positive electrode sheet 151 having a
strip shape, the negative electrode sheet 156 having a strip shape,
and separators 159 interposed between the electrode sheets 151 and
156, which are wound together in a flat shape. The positive
electrode sheet 151 includes a strip-shaped positive electrode foil
152 made of pure aluminum, and positive active material layers (not
shown) each placed on part of each surface of the positive
electrode foil 152. The negative electrode sheet 156 includes a
strip-shaped negative electrode foil 157 made of pure copper, and
negative active material layers (not shown) each placed on part of
each surface of the negative electrode foil 157.
[0026] Each first insulating member 170 made of insulating resin
serves to electrically insulate between the positive extending
member 130 and the battery case 110 (the lid member 113) or between
the negative extending member 140 and the battery case 110 (the lid
member 113). This first insulating member 170 is placed between an
upper surface 131f of a seat part 131 (mentioned later) of the
positive extending member 130 or an upper surface 141f of a seat
part 141 (mentioned later) of the negative extending member 140 and
the battery case 110 (the lid member 113) so that the first
insulating member 170 is elastically compressed in its thickness
direction (a top-bottom direction in FIG. 3). Accordingly, the
through holes 113h and 113k of the lid member 113 are sealed.
[0027] Each second insulating member 180 made of insulating resin
serves to electrically insulate the positive external terminal 137
and the positive bolt 139 or the negative external terminal 147 and
the negative bolt 149 from the battery case 110 (the lid member
113).
[0028] Each positive bolt 139 is a metal bolt including a
rectangular plate-like head portion 139b and a circular columnar
shaft portion 139c (see FIG. 3). The shaft portion 139c includes a
distal end portion formed with screw threads 139d. While the shaft
portion 139c of the fastening bolt 139 is inserted in a through
hole 137c of the corresponding positive external terminal member
137, the head portion 139b is held against rotation in the
corresponding second insulating member 180 (see FIG. 3). In the
battery pack 1 in the present embodiment, this positive bolt 139
and the aforementioned nut 9 are used to fasten the positive
external terminal 137 and the bus bar 2.
[0029] Each negative bolt 149 is also a metal bolt, as with the
positive bolts 139, including a rectangular plate-like head portion
149b and a circular columnar shaft portion 149c (see FIG. 3). The
shaft portion 149c includes a distal end portion formed with screw
threads 149d. While the shaft portion 149c of the negative bolt 149
is inserted in a through hole 147c of the corresponding negative
external terminal 147, the head portion 149b is held against
rotation in the corresponding second insulating member 180 (see
FIG. 3). In the battery pack 1 in the present embodiment, this
negative bolt 149 and the aforementioned nut 9 are used to fasten
the negative external terminal 147 and the bus bar 2.
[0030] The positive extending member 130 made of pure aluminum
(A1050-H24 material) includes the seat part 131, a shaft part 132,
a positive connecting part 134, and a positive deformed part 133
(see FIG. 3). The seat part 131 has a rectangular plate-like shape
and is located in the battery case 110. The shaft part 132 has a
columnar shape protruding from the upper surface 131f of the seat
part 131 and is inserted through the through hole 113h of the lid
member 113 constituting the battery case 110 (see FIG. 4). The
deformed part 133 is a portion continuous with an upper end of the
shaft part 132 and is formed by caulking or riveting, that is,
deformed to extend in diameter into a circular disk shape, and thus
electrically and mechanically joined to the positive external
terminal 137 mentioned below. On the other hand, the positive
connecting part 134 is shaped to extend from a lower surface 131b
of the seat part 131 toward a bottom 110b of the battery case 110
and is welded to the positive electrode sheet 151 (the positive
electrode foil 152) of the electrode body 150. The deformed part
133 before formed by caulking has a cylindrical shape (see FIG. 4),
which is inserted together with the shaft part 132 into the first
insulating member 170, the lid member 113, the second insulating
member 180, and the positive external terminal 137 in this order
(see FIG. 4) at the time of manufacture of a battery, so that a
distal end (a portion which will be the positive deformed part 133)
protrudes more than the positive external terminal 137 out of the
battery case 110. The deformed part 133 is plastically deformed to
be radially widened, thereby fixing the positive external terminal
137 by caulking or riveting to the lid member 113 through the
second insulating member 180 (see FIG. 3).
[0031] The positive external terminal 137 is formed in a nearly Z
shape (a crank-like shape) in side view from a plate made of Al--Mg
aluminum alloy (A5052-H38 material) having a plate thickness T1 of
1.5 mm. This positive external terminal 137 includes a fixed part
137f fixed by the deformed part 133, a connection part 137g
connected to the positive bolt 139, and a joint part 137h joining
the fixed part 137f and the connection part 137g. The connection
part 137g is formed with a through hole 137c penetrating
therethrough. In this through hole 137c, the shaft part 139c of the
aforementioned positive bolt 139 is inserted (see FIG. 3). The
fixed part 137f is also formed with a through hole 137b penetrating
therethrough. In this through hole 137b, the shaft part 132 of the
positive extending member 130 is inserted (see FIG. 3).
[0032] On the other hand, the negative extending member 140 made of
pure copper (C1100-1/2H material) also includes, as with the
positive extending member 130, the seat part 141, a shaft part 142,
a negative connection part 144, and a negative deformed part 143
(see FIG. 3). The seat part 141 has a rectangular plate-like shape
and is located in the battery case 110. The shaft part 142 has a
columnar shape protruding from the upper surface 141f of the seat
part 141 and is inserted through the through hole 113k of the lid
member 113 (see FIG. 4). The negative deformed part 143 is a
portion continuous with an upper end of the shaft part 142 and is
formed by caulking or riveting, that is, deformed to extend in
diameter into a circular disk shape, and thus electrically and
mechanically joined to the negative external terminal 147 mentioned
below. On the other hand, the negative connecting part 144 is
shaped to extend from a lower surface 141b of the seat part 141
toward the bottom 110b of the battery case 110 and is welded to the
negative electrode sheet 156 (the negative electrode foil 157) of
the electrode body 150. The deformed part 143 before formed by
caulking also has a cylindrical shape (see FIG. 4), as with the
positive electrode side, which is inserted together with the shaft
part 142 into the first insulating member 170, the lid member 113,
the second insulating member 180, and the negative external
terminal 147 in this order (see FIG. 4) at the time of manufacture
of a battery, so that a distal end (a portion which will be the
negative deformed part 143) protrudes more than the negative
external terminal 147 out of the battery case 110. The deformed
part 143 is plastically deformed to be radially widened, thereby
fixing the negative external terminal 147 by caulking or riveting
to the lid member 113 through the second insulating member 180 (see
FIG. 3).
[0033] Further, the negative external terminal 147 is formed in a
nearly Z shape (a crank-like shape) in side view from a plate made
of pure copper (C1100-1/2H material) which is the same as the
aforementioned negative extending member 140, and has a plate
thickness T2 of 1.0 mm. However, the plate thickness T2 of the
negative external terminal 147 is thinner than the plate thickness
T1 of the aforementioned positive external terminal 137 (T2<T1).
This negative external terminal 147 includes a fixed part 147f
fixed by the negative deformed part 143, a connection part 147g
connected to the negative bolt 149, and a joint part 147h joining
the fixed part 147f and the connection part 147g. The connection
part 147g is formed with a through hole 147c penetrating
therethrough. In this through hole 147c, the shaft part 149c of the
aforementioned negative bolt 149 is inserted (see FIG. 3). The
fixed part 147f is also formed with a through hole 147b penetrating
therethrough. In this through hole 147b, the shaft part 142 of the
negative extending member 140 is inserted (see FIG. 3).
[0034] In each battery 100 in the present embodiment, the deformed
part 133 of the positive extending member 130 is made of pure
aluminum having tensile strength of 105 N/mm.sup.2 as mentioned
above, the positive external terminal 137 is made of aluminum alloy
having tensile strength of 195 N/mm.sup.2, and the deformed part
143 of the negative extending member 140 and the negative external
terminal 147 are made of pure copper having tensile strength of 245
N/mm.sup.2, respectively. In each battery 100, specifically, the
metal forming the deformed part 133 of the positive extending
member 130 has the lowest tensile strength among the metals forming
the deformed part 133 of the positive extending member 130, the
positive external terminal 137, the deformed part 143 of the
negative extending member 140, and the negative external terminal
147.
[0035] When two or more of the batteries 100 mentioned above are to
be connected together to form the battery pack 1, each two of the
batteries 100, 100 are connected to each other with one bus bar 2.
In the battery pack 1 in the present embodiment, as shown in FIG.
1, the positive external terminal 137 of one of the two batteries
100 is fastened to the bus bar 2, and this bus bar 2 is fastened to
the negative external terminal 147 of the other battery 100, so
that the plurality of batteries 100, 100 (fifty batteries 100 in
the present embodiment) are connected in series.
[0036] Meanwhile, there is a case where the position of the
positive external terminal 137, the negative external terminal 147,
or the bus bar 2 is displaced from an ideal position due to
dimensional tolerance or assembling error of the positive external
terminal 137, the negative external terminal 147, the bus bar 2, or
the battery case 110. In such a case, when one of the two batteries
100 is connected to the other battery 100 by fastening the positive
external terminal 137, the negative external terminal 147, and the
bus bar 2, the positional displacement causes deformation of the
positive external terminal 137, the negative external terminal 147,
and the bus bar 2.
[0037] Herein, as a comparative example of the aforementioned
battery 100, there is shown a battery 200 different only in using a
negative external terminal 247 having a plate thickness T2' equal
to the plate thickness T1 of the positive external terminal 137
(T2'=T1) (see FIG. 5). In this battery 200, the metal materials
forming the positive deformed part 133, the positive external
terminal 137, the negative deformed part 143, and the negative
external terminal 247 are the same as those in the battery 100 in
the first embodiment. Accordingly, in this battery 200, as with the
battery 100, the tensile strength of the metal forming the positive
deformed part 133 is the lowest among the metals forming the
positive deformed part 133, the positive external terminal 137, the
negative deformed part 143, and the negative external terminal
247.
[0038] The following consideration will be given to the case where
the positive external terminal 137, the negative external terminal
247, or the bus bar 2 is deformed in association with the
aforementioned displacement caused when the batteries 200 are
connected to each other in series. In each battery 200, as shown in
FIG. 5, the positive external terminal 137 and the negative
external terminal 247 have the same shape and the positive deformed
part 133 of the positive extending member 130 and the negative
deformed part 143 have the same shape. Regarding the tensile
strengths of the positive external terminal 137 and the negative
external terminal 247, they are relatively high values (290
N/mm.sup.2 and 245 N/mm.sup.2, respectively). Thus, these positive
external terminal 137 and negative external terminal 247 are less
likely to be plastically deformed. The stress associated with
deformation is thus applied to the positive deformed part 133
through the positive external terminal 137 and to the negative
deformed part 143 through the negative external terminal 147. Since
the negative deformed part 143 is made of pure copper having high
tensile strength, it is less likely to be plastically deformed. On
the other hand, since the positive deformed part 133 is made of
pure aluminum having low tensile strength, the positive deformed
part 133 is relatively liable to be plastically deformed due to
stress. Thus, the caulking or fastening state of the positive
deformed part 133 may be loosened. When the caulking state comes
loose, for example, it may deteriorate the sealing performance of
the aforementioned first insulating member 170 placed between the
upper surface 131f of the seat part 131 of the positive extending
member 130 and the battery case 110 with respect to the through
hole 113h of the lid member 113, cause drop-off of the positive
external terminal 137, and other defects.
[0039] In the battery 100 in the present embodiment, in contrast,
the negative external terminal 147 has the plate thickness T2
thinner than the plate thickness T1 of the positive external
terminal 137. Thus, the negative external terminal 147 is more
easily bent and deformed than that in the battery 200 in which the
plate thickness of the negative external terminal 147 is equal to
the plate thickness T2' of the positive external terminal 137.
Accordingly, even when the position of the positive external
terminal 137, negative external terminal 147, or bus bar 2 is
displaced from the ideal position when the batteries 100 are
connected in series, thereby causing the stress due to the
deformation in association with fastening of the positive external
terminal 137, negative external terminal 147, and bus bar 2, the
negative external terminal 147 can be deformed to absorb part of
the stress. By an amount corresponding to the stress absorbed by
the negative external terminal 147, the stress to be applied to the
positive deformed part 133 can be reduced and hence prevented from
becoming plastically deformed. Consequently, the battery pack 1 in
the present embodiment is achieved as a battery pack 1 using the
batteries 100 configured to suppress loosening of caulking between
the positive deformed part 133 of the positive extending member 130
and the positive external terminal 137.
[0040] Furthermore, the electric conductivity .sigma.1 of pure
copper forming the negative external terminal 147 is
.sigma.1=59.0.times.10.sup.6 S/m (20.degree. C.), which is higher
than the electric conductivity .sigma.2 (=37.4.times.10.sup.6 S/m
(20.degree. C.)) of pure aluminum forming the positive external
terminal 137. Accordingly, as compared with the case where the
plate thickness T1 of the positive external terminal 137 is
thinner, the case where the plate thickness T2 is made thinner than
the plate thickness T1 of the positive external terminal 137 can
suppress the resistance increase of the negative external terminal
147. Thus, the battery pack 1 can be provided by using the
batteries 100 entirely having reduced conduction resistance.
[0041] In the battery pack 1 in the present embodiment, the
positive deformed part 133 of the positive extending member 130 is
made of pure aluminum, the positive external terminal 137 is made
of aluminum alloy, and the negative deformed part 143 of the
negative extending member 140 and the negative external terminal
147 are each made of pure copper. Accordingly, the members on the
positive electrode side (the positive extending member 130 and the
positive external terminal 137) and the members on the negative
electrode side (the negative extending member 140 and the negative
external terminal 147) can provide good electrical conductive
performance. Since the metal forming the positive deformed part 133
of the positive extending member 130 is pure aluminum and the metal
forming the negative deformed part 143 of the negative extending
member 140 is pure copper, the battery can be provided with the
positive deformed part 133 and the negative deformed part 143 each
appropriately deformed by caulking or riveting. In addition, the
positive external terminal 137 is made of aluminum alloy (alloy
number A5052H38) and the negative external terminal 147 is made of
pure copper, so that the positive external terminal 137 and the
negative external terminal 147 can also be appropriately prevented
from buckling due to fastening with the bus bar 2.
[0042] The present invention is explained above in the embodiment,
but is not limited thereto. The invention may be embodied in other
specific forms without departing from the essential characteristics
thereof. In the above embodiment, for example, the positive
external terminal 137 and the negative external terminal 147 are
shown in the Z-like shape (the crank-like shape). As an
alternative, for instance, a flat plate-shaped terminal or an
L-shaped terminal may also be adopted. Further, although the above
embodiment shows positive external terminal 137 and the negative
external terminal 147 having the same shape excepting their
thicknesses, these terminals may also have different shapes from
each other.
REFERENCE SIGNS LIST
[0043] 1 Battery pack
[0044] 2 Bus bar
[0045] 9 Nut (Positive fastening member, Negative fastening
member)
[0046] 100 Battery
[0047] 110 Battery case
[0048] 130 Positive extending member
[0049] 133 Positive deformed part (Positive external extending
part)
[0050] 137 Positive external terminal
[0051] 139 Positive bolt (Positive fastening member)
[0052] 140 Negative extending member
[0053] 143 Negative deformed part (Negative extending part)
[0054] 147 Negative external terminal
[0055] 149 Negative bolt (Negative fastening member)
[0056] 150 Electrode body
[0057] 151 Positive electrode sheet (Positive electrode)
[0058] 156 Negative electrode sheet (Negative electrode)
[0059] T1, T2 Plate Thickness
* * * * *